<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .wow {
            width: 200px;
            height: 300px;
            position: fixed;
            bottom: 0px;
            right: 0px;
            background-color: pink;
        }

        .qqq {
            width: 20px;
            height: 20px;
            position: absolute;
            right: 0px;
            top: 0px;
            border: 1px solid black;
            text-align: center;
        }
    </style>
</head>

<body>
    <div class="wow">我是小广告
        <div class="qqq">
            x
    </div>
    </div>
    <script>
        var getqqq = document.querySelector(".qqq")
        var getwow = document.querySelector(".wow")
        getqqq.onclick = function(){
                getwow.style.display = "none"
        }
    </script>
</body>

</html>